Two players (one unnamed, the other known as 1337h4x (leetspeak for "Fucking Nerd") are in a game of Starcraft, with 1337h4x playing as the Zerg race, and the other as either the Terran or Protoss races. 1337h4x Zerg-rushed his opponent, and on finding that he was getting raped, his opponent asked:

<n00b>dude, where are you?

<1337h4x> im in ur base, killing ur d00ds

This meme was then used to death and abandoned by the forums, at which point it was picked up by the rest of the internets and from there became the utterly retarded LOLcats meme.